SST effect on the pre-monsoon intraseasonal oscillation over the South China Sea based on atmospheric-coupled GCM comparison

The role of sea surface temperature(SST)variability in the pre-monsoonal(April to July)intraseasonal oscillation(ISO)over the South China Sea(SCS)is investigated using the Community Earth System Model Version 2(CESM2).An Atmospheric Model Intercomparison Project(AMIP)simulation forced by daily sea surface temperatures(SSTs)derived from a parallel coupled general circulation model(CGCM)run was compared with observations and the mother coupled simulation.In the coupled model,the SST warming leads the peak convection about 1/4 period as in observations.The paralell uncoupled model fails to simulate this phase relationship,implying the importance of air-sea coupling in reproducing realistic ISO.Due to the near-quadrature phase relationship between SST and precipitation ISOs during the ISO events,it is difficult to distinguish the active/passive role of SST from observations alone.Significant correlation in intraseasonal precipitation between the daily SST-forced AMIP and mother CGCM runs indicates that SST plays a role in driving the atmospheric ISO.

Ethics and the Anthropocene Crisis:On the Moral Consideration of Nature

This reflection on the moral consideration of nature begins with two classic arguments of environmental ethics which,while alerting to the growing human pressure on the environment,show the need to rethink the relation of humans and natural world.In my view,Aldo Leopold’s land ethic,seconded by John Baird Callicott and Holmes Rolston III,is the approach in environmental ethics which not only postulates a broader comprehension of the universe of moral concern,but also lays the ground for a new ethical paradigm wherein the human,as a responsible member of the biotic community,has the duty to preserve the integrity,the balance and the beauty of the latter.

Exogenous rare earth element-yttrium deteriorated soil microbial community structure

In this study, we selected yttrium as the representative of REEs to investigate the impacts of exogenous yttrium on soil physicochemical properties and microbiota. The results showed that exogenous yttrium has no significant effect on soil physical properties but a significantly negative impact on soil chemical properties. The results of high-throughput sequencing demonstrate that exogenous yttrium significantly decreases the number of OTUs, ACE, Chao 1, and Shannon indices while increases the Simpson index（P 〈 0.05）, indicating the low soil microbial diversity. The relative abundances of soil microbes are significantly changed at phylum and genus level. Principal component analysis（PCA） showed the significant difference of microbial community between yttrium treatments（YCl_3-250 and YCl_3-500） and non-yttrium treatment（CK） and the similarity of that between YCl_3-250 and YCI_3-500. Proteobacteria and Bacteroidetes are found to be the most tolerant phyla to exogenous yttrium while Verrucomicrobia the most sensitive phylum. Redundancy analysis（RDA） results suggest that exogenous yttrium affects soil microbiota only through changing the soil chemical properties but not soil physical properties, and C/N ratio is the key environmental factor.

On the Shallowing of Antarctic Low-Level Temperature Inversions Projected by CESM-LE under RCP8.5

Temperature inversions are frequently observed in the boundary layer and lower troposphere of polar regions.Future variations of the low-level temperature inversions in these regions,especially the Antarctic,are still poorly understood.Due to the scarcity of observations in the Antarctic,reanalysis data and numerical simulations are often used in the study of Antarctic climate change.Based on ERA-Interim,ERA5,JRA-55,and NCEP-NCAR reanalysis products,this study examines temporal and spatial variations of Antarctic inversion depth in austral autumn and winter during 1979-2020.Deeper inversions are found to occur over the high plateau areas of the Antarctic continent.Based on the Mann-Kendall test,ERA-Interim and ERA5 data reveal that the Antarctic inversion depth in austral autumn and winter increased during 1992-2007,roughly maintained afterwards,and then significantly decreased since around 2016.The decrease trend is more obvious in the last two months of winter.Overall,JRA-55 better represents the spatial distribution of inversion depth,and ERA-Interim has better interannual variability.The Community Earth System Model Large Ensemble(CESM-LE)30-member simulations in 1979-2005 were first verified against JRA-55,showing reasonable consistency,and were then used to project the future changes of Antarctic low-level inversion depth over 2031-2050 under RCP8.5.The CESM-LE projection results reveal that the temperature inversion will shallow in the Antarctic at the end of the 21st century,and the decrease in depth in autumn will be more pronounced than that in winter.In particular,the temperature inversion will weaken over the ice-free ocean,while it will remain stable over the ice sheet,showing certain spatial heterogeneity and seasonal dependence on the underlying cryospheric surface conditions.In addition,the decrease of inversion depth is found closely linked with the reduction in sea ice,suggesting the strong effect of global warming on the thermal structure change of the Antarctic.

Modeling Study of the Efect of Anthropogenic Aerosols on Late Spring Drought in South China

In this study,the mechanisms underlying the decadal variability of late spring precipitation in South China are investigated by using the latest Community Earth System Model version 1 （CESM1）.We aim to unravel the effects of different climate forcing agents such as aerosols and greenhouse gases （GHGs） on the decadal variation of precipitation,based on transient experiments from pre-industry （for year 1850） to present-day （for year 2000）.Our results reveal that：（1） CESM1 can reproduce the climatological features of atmospheric circulation and precipitation for the late spring in South China; （2） only simulations including the forcing of anthropogenic aerosols can reproduce the observed decreasing trend of late spring precipitation from 1950-2000 in South China; （3） aerosols affect the decadal change of precipitation mainly by altering the large-scale atmospheric circulation,and to a less extent by increasing the lower-tropospheric stability to inhibit the convective precipitation; and （4） in comparison,other climate forcing agents such as GHGs have much smaller effects on the decadal change of spring precipitation in South China.

Projection of weather potential for winter haze episodes in Beijing by 1.5℃ and 2.0℃ global warming

Haze episodes become very frequent in Beijing over the past decade,and such trend is related to favorable weather conditions.Here,we project the changes of weather conditions conducive to winter haze episodes in Beijing by 1.5℃ and 2.0℃ global warming using Haze Weather Index(HWI)and data of ensemble simulations from the Community Earth System Model(CESM)low-warming experiment.Compared to present day(2006–2015),the frequency in winter season is projected to increase by 14% for regular haze episodes(HWI>0)and 21% for severe haze episodes(HWI>1)at the 1.5℃ global warming.Projections shows larger increases of 27% for regular and 18%for severe haze events at the 2℃ global warming.The additional warming of 0.5℃ largely enhances the persistence of weather conditions conducive to haze episodes.The increased temperature contrast between near-surface and mid-troposphere in eastern Asia accounts for 57% and 81% of the change in HWI by 1.5℃ and 2℃ warming,respectively.Considering increased haze weather potential caused by climate warming,we suggest that additional efforts in emission reductions of carbon dioxide and air pollution are necessary to mitigate haze episodes in Beijing.